1. Field of the Invention
The present invention relates to an optical connector to be used in a data communication system such as an optical LAN system for an automobile.
2. Related Art
Optical communications play an important role as communication means for supporting the sophisticated information society. This communication means is exemplified by a local area network such as the LAN and is recently incorporated into a mover such as an automobile. This optical communication line is composed mainly of optical fibers and light receiving/emitting element, which have to be connected for constructing the line network. As the method for connecting those elements, there has been known the direct connecting method for fusing the optical fibers or the method using the optical connectors.
When the optical communication network is to be constructed in a stationary structure such as a building, the works are done with dedicated tools or connectors, and by special engineers so that a firm and reliable communication network of little loss is constructed. Moreover, the structure is not encountered by any special problem even if it is more or less complicated.
Under the situation in which the assembling environment is not necessarily excellent as when the optical communication network is constructed in the automobile, however, the components have to be able to be connected simply but reliably unlike the case in which the optical communication network is constructed in the stationary structure. Moreover, it is necessary that the connectors for the components are inexpensive and small-sized.
One example of the connectors of this kind is disclosed in Japanese Utility Model Publication No. 6-33443. In this disclosure, the leading end portion, as called the xe2x80x9cferrulexe2x80x9d, of an optical fiber is held in a plug unit, and this plug unit is fitted in a receptacle unit. Moreover, the connector is provided in the fitted state with an optical element which is positioned on the leading end side of the optical fiber for transferring an optical signal with the optical fiber.
The optical fiber is cut at its leading end portion so that its leading end is exposed to the outside. If the leading end portion of the fiber is either protruded from or positioned flush with the outer surface of the plug unit, however, the leading end of the fiber may be contaminated or damaged, when handled or assembled, so that it cannot transfer the optical signal or increases the transmission loss of the signal.
In the connector disclosed, therefore, the leading end portion of the optical fiber in the plug unit is retracted from the leading end face of a cylindrical unit holding it so that the leading end portion is enveloped in the cylinder unit.
With the aforementioned construction of the prior art, therefore, when the plug unit is fitted in the receptacle unit (or the receiving unit), the leading end portion of the optical fiber and the optical element on the side of the receiving unit are largely spaced. In the disclosed connector of the prior art, therefore, an optical conduction unit of a material or construction similar to that of the optical fiber is interposed between the leading end portion of the optical fiber and the light receiving/emitting element.
In the optical connector of the aforementioned structure, however, the optical signal is transmitted through the boundary between the optical fiber and the optical conduction member and through the boundary between the optical conduction member and the light receiving/emitting element. Therefore, the optical signal may be attenuated by the reflections or scatters at those boundaries. In order to prevent or suppress these disadvantages, the end faces of the optical fiber and the optical conductor member have to be precisely polished thereby to invite another disadvantages that the number of steps of manufacturing the optical connector is increased, and that the cost for manufacturing the optical connector is raised.
For keeping the transmission efficiency of the optical signal satisfactory, on the other hand, it is necessary to adjust the optical axes highly precisely. In the aforementioned structure of the prior art, however, it is obliged to make adjustments to align the optical axes of the three components, i.e., the optical fiber, the optical conduction member and the light receiving/emitting element. Therefore, there arise other disadvantages that the steps of assembling the optical connector become complex and difficult, and that the optical axis adjusting works become factors to raise the manufacture cost.
In the construction of the prior art, moreover, the media for transmitting the optical signal are increased to raise another disadvantage that the transmission loss of the optical signal grows higher. Moreover, the enlarged number of parts raises the cost higher.
An object of the invention is to provide an optical connector having a high optical signal transmission efficienty and an excellent manufacturability, and a method for manufacturing the optical connector.
The optical connector of the invention is provided with: a plug unit holding an optical fiber; and a receptacle unit holding a light receiving/emitting element fitting the plug unit so that it is confronted by the leading end portion of the optical fiber. The light receiving/emitting element is buried in a transparent resin filled therearound, and the leading end portion of the optical fiber is held at a spacing from the outer face of the transparent resin. On the surface side of the transparent resin confronted by the leading end portion of the optical fiber, moreover, there is arranged a lens for condensing an optical signal on the light receiving/emitting element or the optical fiber.
Even if a space is left on the leading end side of the optical fiber, therefore, the optical signal can be reliably transmitted between the optical fiber and the light receiving/emitting element. In other words, no filling member for transmitting the optical signal is required on the leading end side of the optical fiber.
In the invention, moreover, the outer face of the transparent resin filled around the light receiving/emitting element is partially molded to form the lens. With this construction, the transparent resin fixing the light receiving/emitting element can also act as the lens so that the number of components can be reduced to lower the cost.
In the optical connector of the invention, moreover, the leading end portion of the optical fiber can be held with a retraction from the leading end of the plug unit, and the lens and the light receiving/emitting element can be held with an inward retraction from the leading end of the receptacle unit. With this construction, the optical fiber, the lens and so on can be prevented from being damaged, when they are handled before the plug unit is fitted in the receptacle unit.
In the invention, moreover, a prepared lens can be mounted in the receptacle unit, and a transparent resin can be filled between the lens and the light receiving/emitting element. According to this method, the lens need not be worked in the receptacle unit so that the productivity is improved.
The above and further objects and novel features of the invention will more fully appear from the following detailed description when the same is read with reference to the accompanying drawings. It is to be expressly understood, however, that the drawings are for the purpose of illustration only and are not intended as a definition of the limits of the invention.